MAPK1 and colorectal carcinoma: To support and validate the observations seen in Fig. 2, we overexpressed PTPRS in the two CRC cell lines (HCT116 with mutant KRAS and KM12L4A with wild-type KRAS) with CRISPR knockout of PTPRS to determine if the exogenous expression of PTPRS could reduce the phosphorylation of ERK.